Electric elevator.



WWO: I Max J41 67 R. G. SANFORD.

ELECTRIC ELEVATOR.

nrmonmx Hum 1'33. 20, 1912.

Patented July 14, 1914.

2 sauna-sum 1.

70 I an mewlo a: WWW

/0? attozueq R. G. SAN FORD.

ELECTRIC ELEVATOR. APPLICATION FILE-D 313.20, 1912.

Patented July 14, 1914.

2 SHEBTSSHEET 2.

To all whom it may concern:

3.03am: e. saivronn, or YonKEns, NEW YQRK' I ELECTRIC ELEVATOR Specification of Letters Patent.

Application filed February a0, 1912. Serial No. 678,8],9.

Be it known that I, ROBERT a citizen of the United States, residing at Yonkers, in the county of Westchester and State of New York, have invented a new and useful Improvement in Electric Elevators, of which the following is a specification.

I My invention relates to. cont-rolling systems for electric elevators; and more particularly to that type of electric elevator employing a direct current of electricity for:

- both sides of the line and serving to discon- 1 nect the source of current supply from the power. One of the objects ef-my invention is th provision of a simple, practical and efficient 'system ofelectrical control for elevators in which certain parts are made to perform a double function, thereby substantially .re-

ducing the number of parts which would G. SArIFom),

otherwise be necessary, ahd effectinga substantial reduction in the cost of the apparatus as a whole. I

Another object-of my invention is to provide' means for automaticall slowing down an elevator car at anydesired point in its;

travel and varying such-reduction in speed i in accordance with the load. r

' venting a too sudden reversal of an elevator regardless of the load and ineihciency of the operator, therebyinsuring a gradual stoppage of the car without jar or shock, together with a gradual easy start and acceleration, thus preventing (any unnecessary disagreeable shock to the passengers.

Another object of my invention is the provision of non-interference features for ing as suring that the systemot control willeperstrain on the machinery and cablessand any:

- are rotated in one direction or the other at ate under all conditions as itis intended that it shall operate, regardless of the carelessness of the operator or'otherfactors;

Other objects of the invention will appear hereinafter, the novel combinations of elements being pointed out in the appended claims.

electric elevator cont-rolling system embody. ing my invention. The hoisting mechanism itself is not illustrated since the same may be of any desired type or construction and? "forms no part of the present-invention.

Figs2, 3, a, 5 and 6 are fragmentary wirv ing diagramsshowing the motor and certain other circuits corresponding to the vanous positions of the controlling switch in thecar.

Like reference characters denote similar parts throughout all the fi ures.

-Referring to Fig. 1, C enotes the usual Patented July 14, 1914,. i

elevator car in whichis a controlling switch while 11 is a circuit breaker arranged in system of control in the event of excessive currenttlow' therethrough. A main line switch is shown at L, while P designates what 1 term a potential switch and R-is the motor reversing switch. The motor M is preferably compound wound having a shunt field winding designated by D and a series field winding designated by F. Pm accelerating magnet is shown at H and coinprises asingle magnet operating a series of contacts such as 1', 2, 3, 42, 5 and 6, which control the series field F and thestarting', accelerating and stopping resistance G. A stop motionswitch is shown at l comprises a plurality of pairs of switches which are operated at or near the limits or ,car'

travel y means of a rod 12 and cams it, 15 and 16'. Tie mechanism for operating the stop motion switch is not illustrated in detail since the same is well known in the art and is in universal use; it being suffioient to state that the rod 12 and connected cams the limits or car travel by means of a traveling nut on the hoisting drum shaft or in any means of a spring or weight, and is released during the travel of the car by means of an electromagnet. switch is shown at-E and comprises a mag- I net which when energized separates apair of contacts 17 controlling a resistance 18 in series with the shunt field winding of the motor,

tion of the various parts, pointing out the circuitsand showing. how they act on the difi'erent parts to efiect the desired results.

The .electro-magnet switches L, P and R are similar in construction and each one A fast and slow speed I will now'gointo a more detailed descripcomprises a vertically movable or swinging switch arm carrying thereon a plurality of insulated contacts. Corresponding stationary contacts are arranged in alinement with these movable contacts and are adapted to be engaged thereby. Each of these electromagnetic switches is of the solenoid type. comprising magnet windings such as 24, and 26, while the switches P and R are also provided with additional solenoids such as 27 and 28 respectivelywhich are preferably of low resistance. It will be noted that the position of the solenoids 27 and 28 with re-; spect to the magnet cores of the correspond ing switches P and R is such that when the cores are in their lowermost position as illustrated, any current traversing thesesolenoids exerts a pull on the cores in a downward direction, whereas, if the cores are in their raised position, a current I through the solenoids 27 for 28 will not reason for this is j downwardpositionas shown on the drawexert any appreciable downward pull. The; because when the cores are in their lowermost position. they liei within the magnetic field of the-solenoids: but when they are in,t heir raised position the cores are removed from this magnetic field-and the latter has 'no efiect thereon; For this reason- I term the solenoids 27 and 28 5 hold-down coils since they tend when; energized to hold down their corresponding: cores only when the switches arein open or' Assuming the'circui't breaker 11 in closedg pos tion, the operating circuit may be traced from the-F main through a fuse 29g and slack cable switch 30 to a safety- 0 -5 32, 32 of'the car switch S.

emergency switch 31in the car. This switchi being normally in closed position, the cir cuit continuestherethrough to the contacts Leteus further assume thatthe operator the car desires* to go up andthat he moves the switch. lever to the left until the contact segment 33 bridges the contacts 32 and 34. The operating circuit now continues through the car? switch contacts 32 and 34, and wire 35 to the; solenoid 26. From here it returns to the line by way of the wires 36, 37 and fuse 38.

. The solenoid 26 being now energized raises:

its core, thereby closmg thecontacts 39, 40, 41, 42 and 43 and opening the contacts 44, 45 and 46. This operation established the proper motor connections corresponding to an upwardly moving car but the motor does;

not as yet start since the main linecircuit! is still open at the Contacts a the tacts 19 and 21 of the main line. switch L. I The operator next moves the-carswitch-lever still farther to the left until the contact segment 33 bridges the contacts 32, 34-and I 47. A circuit is now closed from the main through the contact 47 and wire 48, stop motion switch contacts 49, wire 50, contacts 4201f the reversing switch R, wire 51,

and'to and through the parallel connected solenoids 25 and 24 of the potential and main line switches respectively, and by the wire 37 and fuse 38 to the main. The 'energization of the solenoids 25 and 24 results in the closing of the switches P and L, thereby establishing a circuit to the motor and brake B.

It will be noted thatthe circuit to the solenoids 25 and 24 includes the contacts 42 of the reversing switch R, hence the switches P and L will not operate unless and untilthe reversing switch R has first moved to closed position to make the proper motor armature connections corresponding to an upwardly moving elevator car.

Under the present conditions, the motorwire 59, armature brush 60, through the armature A to brush 61, wire 62, contacts 40, wire 63, contacts 21 and 19, and throu h the blow out coil 64 to the main. Tie circuit to' the brake releasing magnet 68, may be traced from the line via contacts --22 and 54, contacts 65, wire 66, to andthrough the brake magnet 68, and by the wire 67 and contacts 20,21 and 19 to the main. The shunt field of the motor receives its current through the contacts Y22 and 54, wire 55, wire 69, to and through the field D, wire 70, contacts 17, wire 71, wire 63, and contacts 21 and 19 to themain. The brake'beingvnow released, the motor can start to raise the elevator, both field windings being energized. WVhereas the motor current energized the hold down coil 27 at this time,the latter has no eifect on the switch P since the switch core has alits ready been moved out of the field set up by said coil. The motor will now run at slow speed, since the current flow to its armature and series field winding is limited by the starting resistance G in circuit therewith.

The accelerating magnet H before pointed out has for one of its duties automatically to remove the starting resistance and series a small portion of the starting resistance G,

therefore it depends for its operation upon the C, E. M. 1F. of the motor, I. As the motor field windings from the motor circuit, and

starts, its 0. E. M. F, [gradually increases in value until finally the energization of the accelerating magnet is such that it is enabled to close the contacts 1. This operation short circuits a portion of the starting resistance and permits the motor to increase its speed accompanied by a rise in C. E. M.'F. The

accelerating magnet is consequently further magnetized and. operates to close the contacts 2- ,which short circuit an additional portion of the starting resistance thereby permitting the motor further to, increase its speed. This operation continues, the'contacts being closed one after the other in succession, until finally the last contact 6 is operated which short circuits the series field winding F, and the motor now runs at normal-slow speed as a shunt machine. The condition of the motor circuits in starting and accelerating to slow speed is clearly seen from an inspection of Fig. 2. In order to increase the speed of the motor, the operator in the car moves his switch lever to the extreme left, or untilthe contact segment 33engages the contacts 32, 34, 4:7

I and 79. This operation establishes a circuit to the fast and slow speed magnet switch E, which may be traced from the main to the contacts 32 and 79, wire 80, contact 81,

wire 82, stop motion switch contacts 83 and 84, wire 85, through the winding of switch E, and by the wires 86 and 37 to the main, The switch E is at once energized to separate the contact 17 thereby inserting the resistance 18 in series with the shunt field The resultant weakening of the field strength of the motor causes the latter to increase its speed, and the elevator car now travels at its normal fast speed. i

it will be noted thzit the circuit to the magnet of switch E includes the contacts 81 of the accelerating magnet, and unless these contacts are. closed, it is manifestly impossible to increase the speed of the motor by inserting the resistance 18 in the shunt field unless and until the entire starting resistance as well asthe series field has first been short circuited by the accelerating magnet contacts 1, 2, 3, 4,5, and 6. The advantage of this feature alone is self evident. The motor circuits under the present conditions are clearly seen by referring to Fig. 3.

In order to bring the elevator to rest at any time, the operator moves the car switch lever toward center position until the contact segment 33 runs oil of the contact 79. This results in open .circuiting the magnet of switch E which latter immediately drops its contacts 17, thereby short circuiting the field resistance 18 and strengthening the motor field whichcauses the motor to run at a reduced speed, the conditions of the motor circuit being again as shown in Fig. l. The continued movement of the car switch lever toward center carries the contact segment 33 the switches P and L open their upper con-' tacts. The opening of the switch L disconnects the system from the main line at the contacts 19, 21 and 22, while the opening of the switch P also-opens the motor circuit at the contacts 54 and 57 and closes a local or' dynamic brake circuit around the motor armature by means of its lower contacts. The opening of these switches also opens the accelerating and brake magnet circuits at a plurality of points. This local or dynamic brakecircuit may be traced from the armature brush 60 which is at this time positive and may be considered as through the wire 59, contacts 41, wires 58 and 87, lower contacts 88 of, switch P, wire 55, series field F and starting resistance G, wire 56, hold down .coil 27, lower contacts 89, wire 90, wire 63,

contacts 40, wire 62, to the armature brush 61.

it will be observed that since the accelerating magnet is open circuited at this time, the contacts 1, 2, 3, 4, 5 and 6 are open and the series held and resistance G are no longer short circuited thereby. Furthermore, while the resistance G has had its short circuit removed, that" portion of it lying between the reference numerals 93 and 9t isagain short circuited by the lower contacts 9.. of the switch L, through the wires 95 and 96. The motor now runs as a self extill cited compound generator being driven by the load and the momentum of the parts 7 comprising the elevator machinery, and

sends a current through the series field and that portion of the resistance G which is'not short circuited by the contacts '91 of the switch tion is to efi'ect a brake or retardation on the motor tending to bring it to rest. The brake 3 in the meanwhile has been applied and tendsfurther to efi'ect a friction stop oi the motor. Ttwill be noted that the brake magnet is normally paralleled by a resistance 97 maintained in circuit by the-stop motion contacts 98, 98. The object of this parallel resistance is to retard the action of the brake when it is being applied so that a powerful friction brake may be usedwhich brake will namic brake set up by the motor running as a dynamo, the accelerating magnet is The result of this dynamic so i 5 normally release instantly but will be applied again brought into use. It has been shown that the accelerating magnet circuit was broken at the contacts 23 and 24 when the switches L and P opened and the same im mediately operated to remove the short circuit around the series field F and the startin resistance G. As soon, however, as the switch P has made its lower contacts another circuit is supplied to the magnet winding of the accelerating magnet and the same operates its contacts again to short circuit a portion of the resistance G. This circuit may be traced from the motor bru'sh 60, wire 59, contacts 41., contacts 88, wire 55, resistance 99, contacts 100, wire 101,"contacts 92, wire 102, wire 77, accelerating magnet H, wire 78, Wire 63, contacts 40, and by wire 62 to the armature brush 61. Thus it is seen that the accelerating magnet is connected in series with a resistance 99' across the motor armature. By virtue ofits connection the accelerating magnet will operate its contacts to short circuit more or less of the resistance G in the dynamo bralie circuit depending upon the E. M. F. of the'motor, which in turn is dependent upon its load and speed.

From the foregoing it is seen that I employ the accelerating magnet not only to control the rate of acceleration of the motor in raising or lowering its load, but also to control the stopping of the motor and to vary the reduction of speed in stopping in proportion to the load. This feature I consider of great practical value since heretofore it'has been customary to achieve a similar result'only by the employment of numerous additional switches and electromagnets toge'ther'with their accompanying complications and calling for a motor of special tie-- si I. 7 I Iii connectionwith the operation of the acceleratingmagnet while stopping, it is evident that it would not be desirable to permit the accelerating magnet toshort circuit the entire resistance G, since in that case the local or dynamic brake circuit would be ofextremely low resistance and the current How might under certain conditions become excessive particularly when-the motor is of large size and power. To guard against this possible contingency, I have provided the contacts 92, which are opened assoonas the movablecontacts 4 start to close, and

since the contacts 92 include the circuitof the accelerating magnet when stopping, it is seen that under no conditions can the en tire resistance G be short-circuitedwhile as-for the purpose ofreducin the-poten- --a-ppliedtO", l ii 16 terminals of t] e accelerat- ,fwere'this resistance not used, since the potential of the motor armature at the instant.

' of stopping is comparatively high and the bringingthe motor to. rest, The resistance contacts controlled by the accelerating magnet are arranged to operate when st-artin the motor at a comparatively low potentia so as to short circuit the starting resistance and series field winding in successive steps, thereby efi'ecting a smooth and gradual 'start and acceleration.

It will be observed that the d namic brake effect in stopping is extreme y powerful, much more so than were the motor shortcircuited through a resistance with only the shunt field excited. The reason for this may readily be understood when it is considered that the amount of dynamic brake current is not only that due to the armature rotatin in a normal field produced by the shunt fi eld winding alone, but this current i sent through the series field winding in the same direction as when starting the motor,

hence the actual field strength is considerably in excess of that produced by the shunt field winding alone, and for this reason the (PR loss in the local dynamic brake circuit is substantially increased attended by a powerful retarding or braking action on the motor. In fact I have demonstrated by experiment that a descending elevator car when overloaded fully 50% Will be retarded by this dynamic brake action alone to such an amount that the car will barely creep down the hatchway when the mechanical or friction brake is held off entirely, the load driving the motor as a self excited compound generator. This dynamic braking action is effectively and automatically controlled by the motor itself. acting through the accelerating magnet and will depend upon the load and speed of the motor. For instance in the case of a lightly loaded descendin elevator car as soon as the switches P and I3 are opened to stop the car and the dynamic brake action becomes effective, the retardation of the motor due to the combined action of the friction brake and the dynamic brake may be sufiicient to slow down the ,motor before the potential of the latter has had time to energize the accelerating magnet an amount sufficient to enable the same to operate any of its contacts. The entire resistance G then, excepting that portion of it short circuited by the lower contacts 91 of the switch L, willbe included in the local dynamic brake circuit and the dynamic braking action will be at a minimum corresponding to a lightly loaded car. If the car be heavily loaded andthe operator move the controllin switch to stop position, theload itends tp esp the motor rotating and the mi imum dynamic brake action which we had before in the caseiof a lightly loaded car does not r'etard the s ee'd of the motor so readily." In this case the energization of the accelerating magnet will be such that the latler' is enabled 'to close one or more of the cont'act's 1,2, etc., thereby lowering the resistance in the local or-dynamicbrake circuit and permitting more current to flow which of courseincreases the dynamic brake action on the motor. In this manner the power of the dynamic brake will alwa s depend upon the load conditions which ocourse is most desirable. At the instant of stopping the retardation of the motor is. at first gentle and then increased proportionatel to the load and s eed. One reason for t is is because the friction brake is not instantaneously applied in stopping, since the parallel brake resistance 97 delays the action of the brake. Another reason is because at the instant of stopping, or while the switch is opening its upper contacts and closin its lower contacts, the shunt field circuit 1s open at these contacts, but is almost immediately closed again across the motor armature at the contacts 88 as soon as the switch P has had time to drop by gravity. The shunt field does not immediately die out when its circuit is opened, since the parallel field resistance 109 opposed this action by permitting the field to dischar therethrough. Thus it is'seen that at the time'when the dynamic brake circuit is first establishedthe field strength of the motor is rather weak'hence the retardation at first is very mild, but rapidly increases as the shunt field buildsup and current is sent through the series field windings. This feature is of great practical value'since all lost motion; in. the gears and other parts of the hoistin machine: is gently taken up before the bra e action has reached its full strength, and in this manner all jars and shocks are avoided and the stopping of the car 'is effected smoothly and without any unnecessary strain on the cables or other parts.

.I am aware that the broad principle of employing a dynamic braketo assist in stepping an elevator or other motor is not new,

' more, the system of control is unnecessarily with itfor efiecting. a slow running speed. 1

but .the usual method employs either anadditionaliesistance. in the dynamic brake circuit or an additional high resistance field winding or both. While the usual method is more or-less satisfactory from one standpoint, it involves an additional resistance element which is costly, or else a special motor having an additio'nal'field winding for stopping purposes, which not only is costly vbut otherwise objectionable, since the .(PR

loss therein tends .to overheat the motor,

particularly when the elevator car is fre quently started and stopped, andifurthercomplicated. 1 Then again when an extra field winding is used on the motor for stop ping; purposes, it is customary to use -this same field .winding with a resistance in series This method is almost certain to overheat the motor and extra field resistance and particularly so when the car is operated for any lerugth of lame with the controlling switch in an intermediate or slow speedposition. .Not only is there danger ofoverheating the motor, but there is danger of burning out the extra field and extra field resistance, in which case the extra field would become useless for effecting a dynamic brake stop and the entire duty of retarding and stopping the car would fall upon the friction brake. This method of effecting a slow running speed of the elevator is disadvantageous since the current both excessive, and what is more important, if the load tends to overhaul the motor a reverse current is sent back through the series fieldwinding and the resultant weakening of the motor field strength may be such as to cause a runaway.

other objectionable features since a standard compound .wound motor maybe used to advantage without any change whatever. Furthermore, there is no trouble from overhe may safely do so, since there is no possible danger of overheating the shunt field: winding since it is designed to withstand the main line potential for an indefinite period of time; and there can be no possibility of the load overhauling the motor and cause it to generate a reverse current in the series field windings since at this time the motor is running as a plain shunt motor with short-circuited series field. Furthermore this slow speed will be constant, regardless ofthe load since a shunt wound motor will not vary its speed with varying loads as long asvthe potential at its brushes remains constant. Another feature ofmy invention is in using the accelerating magnet and starting resistance both to start and stop the motor and to elfect both the start and stop in 1 ture' alone tends toward a substantial econ 1 few number of parts are required to do the entire work of controlling the motor: and the systemof control becomes extremely simple minimum amount of electrical wiring, and

time and labor spent thereon.

Turning once more to Fig. 1, it will be observed that the dynamic brake current in stopping, passes through the hold down coil 27 of the potential switch P. Now, since 1 this switch is in its open or lowermost pos1-- consumption and heating of the motor are.

My invention entirely. obviates these and 1 heating the field windings of the motor due speed for any considerable length of time ,omy in cost of manufacture since a very F and free from complications and requiring a a r tio n, the magnetism induced in the core of this switclrexerts a powerful downward pull thereon which holds the current carrying contacts 88, S9 and 100, in firm electrical en gagement with each other and prevents the switch P from again being closed unless and until the current passing through the hold down coil has dropped to a very low amount, or, what amounts to the same thing, until the speed of the motor has been substantially reduced. The function of this hold down coil is therefore not only to hold the current carrying contacts 88, 89 and 100 into firm electrical engagement with each other, but also to prevent the motor circuit from again being closed to the main line until after the motor has substantially come to rest. This feature alone is of importance since it renders it impossible again to start up or reverse the motor While the dynamic brake current is flowing and the motor being stopped. After the motor has stopped, or at most is rotating very slowly, the current in the hold-down coil will be reduced an amount suflicient to permit the -operating solenoid 25 to close the switch again if' so desired, but the solenoid 25 has not sufiicient power to overcome the action of the holddown coil 27 while the motor is being stopped, therefore the latter can never he suddenly reversed or. started again in the same direction.

It will be observed that in stopping with an ascending elevator car, the switches P and L are in open position, while the reversing switch R remains in closed position. The reversing switch will remain closed whether the circuit to the operating coil 26 be maintained at the contact 34 of the car switch or not. That is to say, that upon breaking the operating circuit of the coil 26 at the contact 34, the coil 26 does not become deenergize'd since, while the switch R is in closed position, the contacts 39 and 43 establish a self holding circuit for this coil through the resistances 103 and 104;, across the motor armature by way of the conductors 62 and 59, respectively. By virtue of this self holding circuit it follows that in stopping, the potential of the motor running as a self excited dynamo will energize the coil 26, to maintain the reversing switch in its raised posi-' tion until the potential and speed of the motor has dropped a considerable amount or until the motor has substantially come to rest. This feature insures that the dynamic brake action on the motor in stopping cannot be interfered with by the operator in the car-or by other influence; The motor must come to rest as it is intended that itshall come to rest, without interference of any 'kind. As a further precaution it is observed that as long as the switch R remains in closed position the lowercontacts 4:6 thereon are separated, and, since these contacts inelude a circuit through the car switch contact 105, it follows that the latter is dead and any reversal of the car. switch would have no effect whatsoever on the proper operation of the system. It is immaterial therefore in stopping whether the operator centers his car switch or whether he leaves it in an intermediate position with the contact-segment 33 in engagement with the contact 34:.

The condition of the motor circuit in stopping with an upwardly traveling car is clearly seen in Fig. 4, the load conditions being such that the accelerating magnet has operated one or more of its contacts to short circuit a portion of the starting resistance which at this time is being used as a stopping resistance to absorb the energy of the rotating motor armature and connected hoisting machinery under conditions correspondingto a heavily loaded car. After the motor has come to rest or had its speed reduced substantially to zero, the potential of the armature becomes so low that the current in the self holding circuit of, the reversing switch ceases to flow and the latter moves by gravity to open position and all parts are now in their normal position of rest ready for a subsequent operation from the car switch,

If it is desired to reverse the direction of rotation of themoton and cause the elevator car to travel downwardly, the car switch lcver is moved to the right from its center position until the contact segment 33 comes into electrical engagemen with the stationary contact 105, thereupon a. circuit will be closed from the main through the wire 106, stop motion contacts 107, wire 108, contacts 46 of the reversing switch, and by the wire 51 to and through the windings 25 and 24 in parallel of the respective switches P and L. These switches will operate to close their upper contacts and open their lower contacts, thereby establishing a circuit from the main line to the motor armature, motor' fields,

brake magnet and accelerating magnetv as before'in the case of an upwardly moving elevator car, except in the present case the armature connections are reversed at the lower contacts 44 and 45 of the reversing switch, and the motor will in consequence rotate in a reverse direction. As before, the accelerating ma net will automatically control the short circuiting of the starting resistance and series field winding in graduated steps, so as to' effect a smooth acceleration of the motor to normal slow speed running conditions, while a'fu'rther movement of the car switch lever onto'contact 109 establishes a circuit to the fast and slow speed magnet E, which will insert the resistance 18 into the shunt field circuit, thereby permitting the motor to attain full speed. The

conditions of the motor circuits when runcome to rest.

ning at normal slow speed with the starting resistance and series field windin short circuited are shown in Fig. 5, w ich corresponds very nearly to the conditions of the motor'circuits shown in Fig. 2, where the motoris running at slow speed in the oposite direction, only in the present case the ine current passes through the motor armature in a reverse direction and the motor circuit also includes the hold-down coil- 28 of the reversing switch R. This hold-down coil tends to hold the lower contacts of the reversing switch in firm electrical engagement with each other and prevents the operating coil 26 from raising the reversing switch should the same for any reason be accidently energized as might occur in case of an accidental short circuit or ground on the system.

In stopping with "'a descending elevator car it will be observed that all three switches L, P and R are opened at their upper contacts, and that the dynamic brake circuit includes both of the hold down coils 27 and 28, so that, as lon atingl any apprecia le amount of current it will e impossible to close either the switches as the motor is gener- R or P, hence there can be no possibility of again starting the motor or causing it to reverse. unless and until it has substantially The condition of the motor circuits .whengstop'ping with a descendi elevator car is c early shown in Fig. 6 whic corresponds very nearly with that shown in Fig. 4, only in t e present case-the armature connections are reversed and both of the hold down coils 28 and 27 are in series with the dynamic brake circuit. It will be observed that in stopping an-ascending elevator car, as soon as the same substantially comes to rest, the reversing switch automatically moves to its downward position with the contacts 44 and 45 in electrical engagement respectively. Thus, ifv the car be heavily loaded and the friction brake is unable to hold the load," the latter will tend to drive the motor backward with rapidly increasing acceleration. But since the reversing switch R has at this time closed its lower contacts.

44 and 45, the dynamic brake circuit is closed and so the motor will act as its own brake, as before pointed out, so that the car cannot attain any appreciable speed in a downward direction no matter what the load may be. This feature is in itself of great practical value since it entirely obviates the possibility of a runaway car due to a defective mechanical or friction brake. I

The safety or'emergency switch 31 in the car may be operated at any time to stop the motor by opening the operatin circuit; while the slack cable switch 30, w ich is arranged in the usual manner to operate and openits contactsupon any slack occuring in the cables, effects the same result.

I sometimes parallel the shunt field winding by a hi h resistance element 109 which is often use ul in regulating the s eed of the motor to any desired amount wit in practical limits, and also serves as a safeguard to the shunt field winding in case the circuit of the latter should for some reason become suddenly interrupted, the resulting field discharge bein dissipated and kept from attainlng too. iigh a potential by this parallel resistance.

I will now point out the operation of the stop motion switch I, it being understood from what has been said before that this switch operates only at the limits of car travel in both directions.

Assuming the car to be descending at full speed, and the car switch lever be maintained in its extreme right hand position. As the car approaches its lower limit of travel, the rod 12 and connected cams 13, 14,15 and 16 will rotate in a ri ht hand or clockwise direction. Owing to t e shape of these cams, the switch contact 83 will open first, thereby interrupting the circuit to the fast and slow speed magnet switch E, and causing the latter to short ClIiClllt the resistance 18, thereby strengthening the shunt field and slowing down the motor. Immediately after this has taken place, a further rotation of the shaft 12 effects the opening of the contacts 107 which interrupts the circuit of the operating solenoids 25 and 240i the switches P and L, respectively, thereby permittingthese switch s to open and thus disconnect the motor f om the main line, and putting into operation the dynamic brake and friction brake B. Simultaneously with the opening of the contacts 107, or im mediately afterward, the cam 15 opens the contacts 98, which open circuits the parallel brake resistance 97 and permits the brake B to be applied instantly with full power. At this time the motor will in all probability be completely stopped, but, if for some unaccountable reason the switches and other parts should be disabled and fail to perform their normal functions, a further move ment of the car in a downward direction will cause the cam 16 simultaneously to close the contacts 110 and 111. The closing of the contacts 110 practically short circuits the main line through the main fuses 10 and circuit breaker 11, the efi'ect of which will either blow the main fuses or open the circuit breaker or both, and in any event all current supply is absolutely cut off from the controlling system.

While I desire to insure the opening of .cuit contaln at most a very low resistance,

and I do this by connecting one'of the contacts 110 through the wire 63 and contacts 21 and 19 to the main, while the other contact 110 is connected to the starting resistance G at a point 93, one end of the series field being connected through thelswitch contacts 54 and 22 to the main. Thus it is seen that the closure of the contacts 110 short circuits the line through the series field and a very small portion of the starting resistance, the ohmic resistance of this short circuit being low enough to permit a sufiicient current to flow through the main fuses and circuit breaker to effect the desired result. The closing of the stop motion 'contacts 111 simultaneously with the contact 110 establishes an extremely powerful dynamic brake action, since the dynamicbrake circuit at thistime includes the series field and that small portion of the starting and stopping resistance G lying between the point 93 thereon and the series field. This circuit may be traced from the side of the motor at the brush 61, to the wire .62, through the contacts 44 of the reversing switch R, contacts 111, series field F, a smallportion of the resistance G to the point 93, through the contacts 110, wire 63, hold down coil 28, contacts 45, wire 59 to the side of the motor at the brush 60. e i r I It will beobserved that owing to the low ohmic resistance of the dynamic brake circuit under these conditions, the current generated by the motor acting as a dynamo will be of large amount thereby effecting a maximum dynamic braking action which will rapidly bring the car to a very slow speed so that even should fail to operate'to stop the car the latter will proceed to the end of its run when it will gently bottom without shock or jar since it is moving at a 1 very slow speed. This feature of simultaneously opening the main line circuit and establishing a dynamic brake action of great power I consider of great practical valuein elevator practice.

Heretofore, the stopping of the car has been dependent upon the operation of one or more of the electrically operated switches, and should any one of these switches failto operate at the proper time, which is sometimes the case, the stopping action at the limits of car travel'fails to take'place and the car will in all probability be wrecked and passengers injured or killed. v

With an elevator system arranged according to my invention it is immaterial whether the motor controlling switches stick in the closed position orotherwiseffail to operate at the proper time, since the closing of the sto motion contacts 110 and 111 by the cam 16 is absolutely positive and does not rely upon springs or gravity. Furthermore the closing of these contacts insures that the so sysem will immediately be disconnected from brake action.

though the friction brake motor is in motion. 7

the main line at the circuit breaker 11 or main fuses 10 or both, and that the motor armature will be short circuited through its series field winding and a low resistance element resulting in a powerful and effective My invention absolutely prevents the car from getting beyond control even though the car be descending with a heavy load and the friction brake fail to operate at the lower limit oftravel. The braking action of the motor acting as a *dynamo'is of such ower at this time that the speed of the car is rapidly reduced, and while this dynamic brake action will not bring the car to a dead stop, it will reduce its speed to such an amount that the earv will barely creep along and when the bottom of the hatch way is reached the car will be stopped with ,out injury to itself and without injury or discomfort to the passengers.

- The operation of the stop motion switch when the car is ascending is similar to that just described, excepting that in this case the shaft or rod 12 will be rotated in a left handed or counterclockwise direction, there- 5 by effecting the successive operation of the switch contacts 84, 49, 98, 110 and 111.

The disclosure of my invention herein made is that of the preferred embodiment thereof, and I desire not to be limited to the precise construction of details set forth in said disclosure, as the same may be varied in many particulars without departing from the spirit and scope of my invention.

What I claim, and desire to secure by Letters Patent of the United States is:

1. In an electric elevator, the combination of a' car, a motor operatively connected to said car, a source of electrical supply, a normally closed'reversing switch arranged to reverse the motor connections so as to cause the motor to run in either direction, a potential switch adapted when in one position to close a circuit from the source of 1 electrical supply to the motor, and when in 1 another position to close a local or dynamic brake circuit on the motor, and means for holding said reversing switch against movement ineither direction for both positions of said potential switch during the time the 2. In an electric elevator, the combination of a motor, a resistance, means for connect' ingsaid resistance in series with said motor across the line instarting in both directions and for. connecting said resistance in parallel with said motor'jin stoppin and means for controlling said resistance fioth in starting and stopping. 3. In an electric elevator, the combination .of a motor, a resistance, means for connect.-

ing said resistance in series with said motor across the km in starting-1n both directions and forconnecting said resistance in paralof a motor, a resistance, means for connecting said resistance in series with said motor across the line in starting in both'directlons and for connecting said resistance in parallel with said motor in stopping, and means controlled by the motor for varying said resistance both in starting and stopping.

- 5. In a electric elevator, the combination of a motor, a resistance, means for connecting said resistance in series with said motor across the line in starting in both directions and for connecting said resistance in parallel with said motor in stopping, and means automatically controlled for varying said resistance both in starting and stopping.

6. In a electric elevator, the combination of a motor, a resistance, means for connecting said resistance in series with said motor across the line in starting in both directions and for connecting said resistance in parallel with said motor in stopping, and means controlled by the varying potential ofthe motor armature for short-circuiting said resistance both in starting and stopping.

7 In an electric elevator, the combination of a main line circuit, a compound wound motor, a resistance, an electro-responsive de vice adapted when in one position to connect the series field Winding, motor armature and said resistance in series across the main line, and when in another position to connect the motor armature, series field Winding and said resistance in a local or dynamic brake circuit, and means controlled by the motor both in starting and stopping for varying said resistance for both positions of said electro-responsive device.

8. In an electric elevator, the combination of a compound wound motor, of a main line circuit, a resistance means for coiinecting said motor, series field and resistance ina series circuit across the line, means for short circuiting said series field and resistance in starting the motor, means for connecting said series field and resistance in series with of a motor, a resistance arranged to be connected in circuit with. the motor both in starting and stopping'in both directions and means controlled by the motor in accor ance with the load for varying said resistance both in starting and stopping.

. 10. In an electric elevator, the combination-of a motor, a resistance arranged to be connected in circuit with the-motor both in starting and stopping in both directions, and means for varying said resistance in accordance with the load on said motor both in startin and stopping.

11. 11 an electric elevator, the combination of a motor, a single resistance used both for starting and stopping the motor in both directions of rotation, and means controlled by the motor in starting and stopping for varying said resistance.

12. In an electric elevator, the combination of a motor, a resistance used both for starting and stop ing said motor in both directions of rotatlon, and an electro-responsive device controlled by the motor arranged gradually to short circuit said resistance both in starting and stopping.

13. In an electric elevator, the combination of a motor, a resistance used both for starting and retarding the motor, means controlled by the motor for short circuiting tion of a compound wound motor, of a resistance, electro-magnetic switch apparatus arranged to connect said resistance in series with the motor in starting and for connecting said resistance in parallel with a circuit comprisin the motor armature and series field win ing in stopping, and means for varying said resistance both in starting and stopping.

15. In an electric elevator, the combination of a, compound wound motor, of a resistance, electro-magnetic switch apparatus arranged to connect said resistance in series with the motor in starting and for connecting said resistance in parallel with a circuit comprising the motor armature and series field Winding in stopping, and means controlled by the motor for varying said resist ance both in starting and stopping.

16. In an electric elevator, the'combination of a compound wound motor, a resistance, a main line circuit, switch mechanism arranged to connect said motor and resistance in series across the main line in starting, and for connecting the motor, seriesfield Winding and resistance in a local or dynamic brake clrcuit in stopping, and means operated by the motor for varying said resistance both in starting and stopping.

17. In an electric elevator, the combina-.

tion of a motor, of a resistance used both for starting and stopping said motor, an electro" responsive device arranged automatically to control said resistance, an additional resistance, and means for inserting said additional resistance in series with the magnet of said electro-responsive device during the operation of stopping the motor.

18. In an electric elevator, the combinatravel, and automatic means controlled by the motor for effecting a quick a plication of said lorakewhen the. car excee s its normal travel in either direction.

20. In an electric elevator, the combination of a car, a motor operatively connected thereto, a main line circuit, a circuit-interrupting device'connectedin said main line circuit, and means for causing an abnormal flow of current through said circuit interrupting device to effect the operation of the latter when the car exceeds its normal limits of travel,

21. In an electric elevator, the combination of a car, a motor operatively connected thereto, a main line circuit, a switch ada ted when in one position to close a circuit to said motor from the main line, and when in another pos tion to close a local or dynamic lhralre circuit around the motor, and means for causing an abnormal flow of current to efiect the opening of said switch to close the local or dynamic brake circuit when the car exceeds its normal limit of travel.

22. In an electric elevator, the combina-- tion of a car, a motor operatively connected thereto, a main line circuit, a switch adapted when in one position to close a circuit to said motor from the main line, and when in another position to close a local or dynamic brake circuit around the motor, and means.

controlled by the car for causing an abnormal flow of current to effect the opening of said switch to close the local or dynamic brake circuit when the car exceeds its normal limit of travel.

23. In an electric elevator, the combina-. tion of a car, a motor 0 eratively connected thereto, a reversing switch for the motor, electromagnetic means for moving said; switch in one position and for permitting gravity to move it in another position, a.

ynamic brake circuit for said motor which is established whenever said reversing switch is in its gravity operated position, and means for maintaining said switch against movement in either direction while the said motor is in motion.

In testimony whereof, I have signed my name to this specification in the presence of two subscribing witnesses.

ROBERT e. SANFORD.

Witnesses: I

Jaime G. Barnnnn, ERNEST L. GAJZE, Jr, 

